Limpeza diária e filtros HEPA a bordo em voos desde São Paulo Congonhas para Istambul
O KAYAK é um buscador de viagens. Isso significa que vasculhamos a web até encontrar os melhores preços para nossos usuários. Processamos anualmente mais de 2 bilhões de pesquisas de voos, o que nos permite exibir uma grande variedade de preços e opções de voos de São Paulo Congonhas para Istambul.
A ferramenta de previsão de preço de voos do KAYAK utiliza dados históricos para determinar a probabilidade de o preço de um voo de São Paulo Congonhas para Istambul mudar dentro de sete dias. Assim, os viajantes podem saber se esperam ou reservam agora.
As tarifas do KAYAK Mix permitem combinar passagens somente de ida para economizar na comparação com uma passagem tradicional de ida e volta. Dessa forma, você pode voar para Istambul com uma companhia aérea e voltar para São Paulo Congonhas com outra.
Às vezes, é possível ser um pouco flexível quanto às datas de uma viagem. Se suas datas preferidas tiverem alguma margem de manobra, o recurso datas flexíveis mostrará todas as opções ao voar de São Paulo Congonhas para Istambul até 3 dias antes ou depois das datas selecionadas na pesquisa. Assim, você pode escolher os voos que mais lhe agradam.
Pontuações baseadas em avaliações de usuários do KAYAK
Contras: "KLM lost my suitcase and did not deliver it until three days later... They refused to compensate me for having delivered the bag with broken articles inside (A pair of Rayban Wayfarers!)"
Contras: "Very nice crew and great food"
Contras: "Bigger seats the new ones are way to narrow"
Prós: "Decent price for economy comfort seat, 4A."
Contras: "The flight was delayed about 80 minutes and they did not informed until when I got to the Airport. I could have stayed more at home instead of the terminal. They have also changed the boarding gate.."
Prós: "Klm's consistantly high standards in everything they do."
Prós: "A Gol faz o estilo low cost então não espere grande coisa."
Contras: "O atendimento da tripulação."
Contras: "A mesa de bordo e a bandeja de refeições não estavam firmes. A bandeja escorregava o tempo todo."
Prós: "Great airline"
Prós: "Infelizmente não tive nada que me agradou, tanto que não voltarei a voar nesse companhia."
Contras: "Tudo, o atendimento ao cliente é péssimo."
Contras: "Tudo tem que ser melhorado"
Prós: "The aircraft"
Contras: "No overbooking next time!"
Prós: "O voo saiu adiantado, pois todos ja estavam no aviao."
Prós: "Refeições de alto nível"
Prós: "Seats super comfy. Ended up with 3 seats to myself that formed a bed for the lap Uk to NZ. Very nice!"
Contras: "Acomodação na área econômica, espaço entre as poltronas."
Contras: "Delays, took my hand luggage into the hold,"
Contras: "Dozens of high school students screaming and climbing onto seats, crew did not intervene."
Prós: "Filmes à disposição"
Contras: "Auxiliei no atendimento a um passageiro que passou mal, e a comissária me informou que iria receber um desconto numa próxima viagem, e que receberia tal desconto em meu e-mail, porém não o recebi. Meu nome: ELISABETE DE SOUZA PINHEIRO. Preenchi e assinei em seu tablete inclusive."
Prós: "The crew are amazing! Attentive and friendly."
Contras: "The seats could have been bigger."
Prós: "well mannered and attentive crew - good supply of complimentary food/drink - good over all comfort"
Contras: "boarding was running very far behind - considering this is mainly a hub operations carrier - resulted in several passengers missing their connecting flights -"
Prós: "Crew was amazing, seats were comfortable with enough leg space even without choosing extra space seats. It was my childhood dream come true to fly with KLM. It was really an exciting trip for me, just that it was short."
Contras: "Well, for me everything was on point. Those who have never travelled with KLM, I would encourage them to do so and I’m sure they will not regret."
Prós: "I love the food"
Prós: "A tripulação fez o quê pode para nos ajudar!"
Contras: "Devido à um pouso de emergência fomos forçados a pemanecer dentro do avião por 8 horas!"
Prós: "Very pleased with KLM - efficiency all round and especially the baggage handling at Schipol swhere I had 20 minutes to transfer and my baggage came back with me to the UK which is no mean feat given the hustle and bustle of such a large airport"
Contras: "No downsides at all"
Prós: "Sistema de entretenimento é um destaque a parte! Opção de internet à bordo (pagamento a parte), refeição de excelente qualidade!"
Prós: "Os acentos são os padrões da classe econômica, mas um destaque que merece respeito é o sistema de entretenimento/multimídia, além da opção de internet à bordo (pagamento a parte, caro, mas para quem precisa, é ótimo). Sempre tem algo na galley para quem gosta de esticar as pernas!"
Prós: "The crew was very nice"
Contras: "Uncomfortable seat but it’s only a 1 hour flight so not a big deal."
Prós: "The flight arrived a few minutes early."
Contras: "The plane was extremely old and in poor repair. The seats were extremely close together. The inflight entertainment system, wifi and passenger electric outlets were all non-functional. Even the wastebin in the lavatory was full and an extra bag was put on the floor."
Prós: "Do serviço de bordo"
Contras: "Gostaria que tivesse uma tradução para português, através do sistema de multimídia, seja por legenda ou áudio, nas orientações no decorrer do voo"
Prós: "We got to Amsterdam on time"
Contras: "1. Paying for the seats we chose...that will never happen again...I'll fly another airline first. 2. The food was terrible. I have flown KLM for years, this was not what I expected. 3. The plane was very dirty"
Contras: "My suitcase didn't come with the airline."
Prós: "MCR airport Mert & Greet parking was smooth and efficient."
Contras: "Flight was delayed 2 hours due to bad weather. Additional baggage payment to Air Baltic did not show up on the KLM system and we had to pay again. Nowhere to address this with Air Baltic even in Tallin. Handlers seem uninterested and refer us to ‘the website to address the issue.....’"
Prós: "Short flight and being able to escape from drunk belligerent Passenger on previous flight"
Contras: "Flight was delayed, landing at vce took an additional 10 minutes due to no one at the jet way. Luggage service was very slow"
Contras: "Our lougage did not arrive"
Prós: "Staff very pleasant"
Contras: "Evening snack was not the greatest breakfast was pretty food"
Prós: "Arrieved on time!"
Contras: "Dem entretenimento"
Contras: "Very slow service at checkin, was not even available when I arrived at the airport"
Contras: "Ter que caminhar muito no chegada ao Galeão"
Prós: "Arrived early!"
Contras: "Boarding seemed disorganized."
Contras: "Do conforto no banco do meio da fileira de 3(três) pessoas"
Prós: "He missed it due to having a 32 minute layover, which he ran all the way to board."
Contras: "he had no choice but to look at the closed door of his flight, and wait an additional 7 hours and they didn't even give him a voucher for food. I'm his mother, I'm currently visiting family in Scotland, so couldn't help him much. I'm pretty disgusting and disappointed by the whole experience."
Prós: "Excellent very good"
Contras: "Everting so good ex"
Prós: "Atendimento e alimentação"
Contras: "Nada a mencionar"
Prós: "Equipe de bordo muito simpática"
Contras: "Cadeiras apertadas nas laterais O vôo faz uma parada de pouco mais de 1 hora em Kuala Lumpur, Malásia, porém isso não foi avisado quando fiz o check-in no Brasil."
Prós: "Como haviam cadeiras vazias no vôo consegui voar com muito conforto."
Prós: "Good flights. Good prices."
Prós: "El entretenimiento"
Contras: "Demasiadas mascotas sin posibilidad de descanso. Un gato en ej asiento del frente que no dejó de hacer ruido y dos asientos atrás un pero en la misma situación. Debería tomar más medidas para el viaje de mascotas"
Prós: "The crew was perfect"
Contras: "No wi fi on the plane."
Contras: "This airline charges for everything, and after you pay once, they try to charge you again, and again, and again (four different people tried to charge me 4 different times for my two checked bags). And they lost the record of my payment, so I had to show 4 times the Amex receipt showing that I had paid before. It took 45 minutes and 4 non receptive agents for me to get my luggage checked. British Airways is significantly better."
Contras: "Air France’s apathy towards its customers is shocking. Traveling with three children , our flight was delayed by 3hrs resulting us arriving in Paris after 1AM. With the airport shuttle(CDVAL) to our airport hotel closed, they offered no assistance despite of my request. Simply asked us to take a taxi (when all taxi stands are abandoned at 2AM). Beware if traveling with family."
Prós: "Crew were very good."
Contras: "No vegan food available."
Contras: "Seat recline was broken- wouldn’t hold position."
Contras: "tout est à revoir !"
Prós: "Crew attentive. The delay was due to airport conditions in FCO, cannot be blamed on Air France."
Contras: "Food. For a 2-hour plus flight, from 11am to 1:30pm, we got 20gr pretzel sticks. This is ridiculous. Don't pretend you are not low-cost! Formerly, before the Joon failed (thank God) venture, Air France had real sandwiches around that time of the day on that line."
Prós: "The seats were spacious and the crew was wonderful. The crew actually made the long flight more tolerable. Will seek out Delta/Air France for further international flights."
Prós: "Flight attendant was rude to my non French speaking 12 year old. He ripped his charger out of the USB port and threw it at him."
Contras: "TSA was sketchy and gave a FULL search, part down, etc. I kept asking and the excuse kept changing. Final excuse ridiculous! Flight attendant could have not treated my son as he way he did. I was unaware that the usb cord being inputted during taxiing As was my son. He was horrible to him!!"
Contras: "Poor service. Terrible food. Aging aircraft. Terrible in-flight entertainment system. Really not good AirFrance."
Contras: "Check in process running smoothly and better announcement of gate change"
Contras: "Great experience"
Prós: "Genial ! Comissários fantásticos ! Alegres e educados ! Parabéns ! Comida nota 10."
Contras: "Nunca havia visto um time de comissários tão educados , prestativos , felizes e que tornam a viagem uma excelente experiência ! Parabéns !"
Contras: "Not really an Air France flight, AF not interested in taking care of their frequent fliers."
Prós: "Air France personnel is always really helpful"
Contras: "Food and comfort in short haul are not the best - but the flight is short..."
Prós: "Do conforto, comida e os atendentes muito educados."
Contras: "A falta de creme para as mãos na necessaire, ou ao menos no lavatório. As mãos ressecam muito em voos longos."
Prós: "Crew was nice movie selection was good."
Contras: "Plane was late which caused a 5 hour layover in Paris CDG. Food not very good. Entertainment system clumsy to operate."
Prós: "I was given a great seat and the food was OK- not the Air France food of 5 years ago but still good"
Contras: "I didn't really use the in flight entertainment - the usual movies, tv etc"
Prós: "Cheap ticket"
Contras: "The fact that you cheapskates don't allow credit or refund is downright usury. I didn't take that flight because of medical issues that caused me to cancel my trip 2 weeks in advance. I pleaded with you to be able to take a credit, to no avail. You lost a customer."
Prós: "SFO - CDG (Air France) was a great journey in all respects. But the one major reason for that was, the middle seat was empty. I was so fresh after the journey, would definitely recommend this flight to anyone."
Contras: "The flight was delayed by atleast 45 mins and therefore had to rush at the CDG airport to catch the next flight."
Contras: "I was treated like I am not supposed to ask for food and they had one choice of meal for me while they had 2 for the rest."
Prós: "Great service and food."
Contras: "Tv screen is resolution is to low. Hard to see details."
Contras: "Flight was delayed by 1h30min, so we arrived very late"
Prós: "I like fly attendant who served us meal"
Contras: "I didn’t like that space between each seat is small"
Contras: "We paid for Business Class from JFK to TLV. The flight to Tel Aviv was in a small plane with 3 across seats that hardly reclined. We are most unhappy and will complain to American Express Platinum Card."
Prós: "I liked the crew, they were professional and tried their best"
Contras: "The flight was a chartered flight . Air France informed us that due to cabin crew shortage they couldn't operate an air france flight and hence they hired Air Belgium. Whilst the crew were nice , the actual plane was old and creaky. It wasn't up to the standards expected of Air France. They could have done better in getting a plane up to standard. A lot of the passengers were disappointed ."
Prós: "Cordialidade da tripulação."
Contras: "Assentos demasiadamente inconfortaveis para um vôo de longa duração. Comida de baixa qualidade."
Prós: "Sometimes you get surprised, with this specific flight, we had an excellent young and perfect cabin crew. Thanks, Joon!"
Prós: "Great hospitality. Champagne as apero, cognac as digestif. Excellent on board entertainment. Comfy pillow and blanket."
Prós: "The airplane have great entertainment system. The cabin crew are very nice."
Prós: "Service was great, flight was on time and I really enjoyed everything"
Contras: "Little turbulence but overall it comes as usual so it was worth the flight"
Prós: "Os assentos e a organização da tripulação são ótimos."
Contras: "Não há entretenimento, então recomendo apenas voos curtos."
Prós: "The crew was very nice and helpful."
Contras: "We ordered a vegetarian meal. However, the vegetarian option offered to those who did not order a special meal looked better than the vegetarian option that we received."
Prós: "The check in process was much better in the CFG airport than SFO. Very organized."
Contras: "The food was mediocre on this flight. The seats also are surprisingly uncomfortable."
Prós: "Pretty decent"
Contras: "Not much"
Prós: "No issues, quick trip, friendly staff, comfortable ride..."
Prós: "Atendimento muito bom, todos simpáticos, voo tranquilo"
Prós: "It didn't take longer to board! Crew with great attitude Take off and landing were just great"
Contras: "My sandwich, it contained too much pepper, I mean too muuuuuch My narrow seat No entertainment"
Prós: "We were on a 9 hour flight which is pretty exhausting on its own. However, Air France provided you with a pillow and blanket, as well as headphones, so that you can make the best of the long trip."
Contras: "The chairs, for whatever reason, after just not that comfortable. Too squishy and they make noise when you adjust your position. I fidget a lot on flights so I felt like I was making a lot of noise. Also the plane didn't have cold air, do you get toasty pretty quick."
Contras: "The leg-space is very narrow The chair is very tiring No entertainment at all Food was tasteless But most surprising was that we were on stand by for our connecting flight. Though we bought the tickets months ago and we got our luggage checked in all the way to the final destination."
Prós: "Duração do vôo"
Contras: "Desconforto da poltrona."
Prós: "Atendimento à bordo."
Contras: "Conforto à bordo e falta de educação do passageiro da poltrona 48 L. Infelizmente, pela segunda vez minha bagagem é extraviada em Paris. Dessa vez, foi parar em Amsterdã e do chegou à Riga no dia 16, às 22:15 h."
Contras: "bad smell around my seat"
Prós: "Atendimento dos comissários, estado geral da aeronave."
Contras: "A econômica é realmente muito apertada, e o conforto para uma viagem noturna é muito ruim. A comida estava bem mal preparada (pasta era um bloco só grudado, o omelete estava todo escuro por excesso de cozimento)."
Contras: "Turn on AC. Bigger seats. Better food. Serve drinks more than twice on an 8 hour flight. Actually have soap in the soap dispenser in the bathroom."
Prós: "A tripulação poderia cuidar mais das pessoas e não ficar foçada na venda de produtos. Não foi servido nem um cafezinho e nem um copo de água no voo de Amsterdã a Madri."
Contras: "Poderia ter mais espaco entre as cadeiras."
Prós: "The flight was on time and the staff were great."
Contras: "The seats are quite worn, with crumbs and drips here and there from previous flyers, and the magazines very dog-eared - makes you feel a bit like you don't want to touch anything."
Prós: "The flight wasn’t bad"
Contras: "The checking, customer service, Air Europa website and food was a disaster."
Prós: "Tudo. Ok"
Contras: "Tudo ok"
Contras: "Li vários comentários nos mais diversos lugares que a companhia era péssima, então me preparei para o pior. Que bom, pois tive a grata surpresa de voar em um avião novo, cheiroso e com bom entretenimento. Comida ok, foram dois serviços. Vôo tranquilo, tripulação não é simpática, mas é atenciosa. Cur"
Prós: "The crew and service, the overall flight was good."
Contras: "The waiting time, boarding,"
Prós: "The price!"
Contras: "Never on time!"
Prós: "Embarque na hora e de forma tranquila, saída e chegada antes do horário, boa comida e tomada para carregar o celular."
Contras: "Não consegui fazer o check in pelo celular."
Prós: "NADA!! PÊSSOMO, TUDO!"
Contras: "A aeronave, não deveria está em uso!!! TERRÍVEL! Tudo ruim!! Ponham uma aeronave descente para fazer MADRID -PORTO! A Aireuropa, tenho certeza, tem aeronave descente, pôs jã voei com a AIREUROPA, no ultimo mês de Março! Nunca tinha voado em um amontoado de ferro velho, como essa aeronave de hoje!"
Prós: "Apenas a pontualidade!"
Contras: "Tudo na aeronave, comida"
Contras: "There was a 2 hours delay that caused me to miss my other flights, without any compensation or at least apology"
Prós: "Cheap prices"
Contras: "Air Europa is is budget airline, and things you expect to not always work. I could not check online, because the web site did not work. When checking in at the airport, I paid extra for exit and bulkhead row seats for my family, after which the agent told me that the seas were in different parts of the airplane. The agent was not willing to refund the money I paid and give us ordinary seats. Apparently, with Air Europa, money goes only one way. Still, cheap, so may be attractive."
Prós: "Flight itself was good, no options for emtertainment tho"
Contras: "Check in was terrible at the terminal. Poor signs or personnel to guide the checkin lines caused fights among passengers and confusion where to check in from. Ground attendants arrived and did not inform the crowd right away causing dangerous physical and verbal fights among people making different lines. Terrible situation"
Contras: "40 minute delay, slow boarding, inoperative lavatory, sitting in row 4 and crew dis not allow me to use forward lavatory, dis not bring requested food"
Prós: "The effort of Air Europa crew to try to accommodate us in seating request"
Contras: "1) Aircraft overall conditions. Aircraft interior needs to be refurbished. The quality of the food served was under normal standards. 2) Boarding of the aircraft was not well organized 3) Aircraft departure scheduled time shown on the screens differed from actual boarding pass printed time thus creating confusion."
Prós: "Pequena vantagem de preço em relação a outras companhias. Foram pontuais."
Contras: "Não é possível fazer check-in online, que foi demorado antes do embarque. A companhia não informa com exatidão o terminal e o gate de embarque até 2 horas antes. O assento bastante apertado, as refeições muito simples. Foi complicado planejar a ida ao aeroporto sem essas informações."
Prós: "Avião novo 787 muito bom"
Contras: "Desembarque demorou muito"
Contras: "Embarque!!! Péssimo, desorganizado, confuso, pessoas despreparadas"
Contras: "Entretenimento era muito fraco"
Contras: "No wheel chair in Madrid as REQUESTED"
Prós: "Very helpful crew. Courtious"
Contras: "Food could be better in flight."
Prós: "good service"
Contras: "cramped chairs and an attached box under my seat limiting foot space. Also i didn't like having to plug into their wifi and pay a fee.so i didn't use it. couldn't figure it out either since my phone had been stolen at the MAD airport and all I had was a kindle fire."
Prós: "O embarque foi muito rápido e fácil. A comida a bordo estava boa e o espaço entre as pernas era bom."
Contras: "O avião era muito antigo, não tinha sistema de multimídia individual. Um absurdo para um voo transatlântico. No lugar disponibilizavam acesso ao acervo de filmes através do Wi-Fi da aeronave ou utilização do mesmo conectado à internet, porém com valor surreal. 20 megabytes de dados por 7 euros?!"
Contras: "Not only did we board an hour late but we were basically held hostage for over 3 hours inside the airplane due to navigation difficulties. We were in the middle of the ramp and little information was given. Needless to say I missed my connecting flight. A total nightmare."
Prós: "A tripulação tem uma boa qualidade e tenta oferecer o padrão das outras companhias aéreas. Piloto parece ser muito experiente, decolagem e pouso perfeitos sem sobressaltos."
Contras: "Avião velho. Assentos com mal cheiro, estofamento desgastado e fino. Pouco espaço entre os assentos. Entretenimento antigo e sem variedade. Poderiam avisar com alguns dias de antecedência sobre a oferta de streaming no avião. Assim como disponibilizar pontos de recarga de celulares e tablets nos assentos. Em resumo o avião funciona sem problemas, mas o conforto deve ser atualizado urgentemente."
Prós: "Do atendimento da tripulação! Todos cordiais e atenciosos, além de muito pacientes."
Contras: "Da falta de cuidado com os aviões e da desorganização no dia que perdemos a conexão e demorou demais para providenciarem um ônibus para o hotel e na volta do hotel o ônibus nos deixou no terminal errado. Coisas simples, mas que demonstram uma falta de cuidado com os processos."
Prós: "The Embraer is a great regional aircraft."
Contras: "There are plenty of air bridges to use at Porto airport, but AirEuropa chooses to use a stand that requires busing passengers from the terminal and back. No IFE."
Prós: "It was really comfortable and the food was great, the crew was really nice."
Contras: "There was only like 8 old movies and none of them loaded so I couldn't watch anything. And the Wi-Fi super expensive."
Prós: "O check-in e o embarque foram pontuais e razoáveis. Apenas."
Contras: "Péssimos espaços entre poltronas e reclinação. Não tinha multimídia individual, para entretenimento deveria ser usado o próprio smartphone via wi-fi do avião, que só disponibilizada poucos (5) filmes ruins. Não há tomada para carregamento e o banheiro é mal conservado. Nunca usaremos novamente. Não vale o preço."
Prós: "Voo com avião novo, com espaço OK entre poltronas para o trecho."
Contras: "Tripulação mal treinada e antipática."
Contras: "Delayed for full day today n Madrid did not get put on the next flight but flights that were much later:("
Prós: "No frills, had a laptop based entertainment system."
Contras: "Food was just OK."
Contras: "Sat sweltering on tarmac with doors open. All passengers sweating"
Prós: "Preço mais baixo que encontrei nas pesquisas."
Contras: "Fila para check in. Fone de ouvido por 3 euros."
Prós: "Fast, convenient flight from Boston to Madrid. Good value for price. He"
Contras: "Had paid extra for confirmed seats, which we were told at check-in were not available. Told that the plane was full and to keep boaipasscfor refund."
Prós: "Two meals and some in-flight entertainment. Not too bad. You can order a special meal (such as vegetarian) by calling the service center, and it's served first."
Contras: "Red-eye flight, econ seat uncomfortable for sleeping. Fewer entertainment options than other airlines"
Prós: "No delays! Accurate"
Contras: "Boarding process they start from back rows first"
Prós: "Wide body aircraft."
Contras: "no service, bad food, no individual tv screens, no choice movies"
Prós: "Arriving plane was late and then there was added lateness because of a bag put on the plane without owner getting on plane -- perfectly fine otherwise, just a bit disorganized."
Prós: "The crew was pleasant."
Contras: "When I flew from Boston to Madrid, both TV sets in my row were broken, no signal at all. On my return flight from Madrid to Boston, I paid extra for a window seat in the front of the plane. I was in seat 16c, there was no window and again the TV was broken!! The flight crew found me an isle seat near the rear of the plane where the TV worked."
Prós: "It was an ok flight."
Contras: "The line at the airport, there were no tv for movies or entertainment of any kind (besides paying for an iPad or internet), and the chair didnt laid back."
Contras: "Flight was cancelled without explanation. We scheduled flight was also seriously delayed. Flight to Barcelona was siginifivantly delayed as well. Poor communication to the passengers. I'll never fly Air Europa again. Moreover, I'll recommend my friends to not fly this airline as well."
Prós: "Crew inside"
Contras: "Airport gate unprepared for wheel chairs and strollers. No elevator in gate area."
Prós: "We had no problems with boarding on time or checking our bags. Some reviews were upset about the in-flight entertainment (or lack thereof) but Netflix has a download option now and I pre-planned and binged an entire series on the flight. I didn't eat the food on the trip to Europe but on the way home I had the veggie pasta, wine, coffee and the pizza snack and it was all basically on par with other airplane food I've had. The attendants were also all fantastic and polite and helpful."
Contras: "The seats could be more comfortable and I don't love paying to choose my seat but these are small things in the grand scheme of it all."
As companhias aéreas que voam desde São Paulo Congonhas para Istambul implementaram medidas de segurança adicionais e ajustaram suas políticas para melhor acomodar os viajantes. As políticas variam de acordo com a companhia.
Limpeza diária e filtros HEPA a bordo em voos desde São Paulo Congonhas para Istambul
Máscaras obrigatórias e fornecidas a bordo em voos desde São Paulo Congonhas para Istambul
Distanciamento social nos assentos
Assentos do meio não disponíveis para reserva em voos desde São Paulo Congonhas para Istambul
Teste de anticorpos e triagem de sintomas em voos em voos desde São Paulo Congonhas para Istambul
Sem taxas de alteração. Pesquise voos flexíveis desde São Paulo Congonhas para Istambul